PURPOSE: To show the effect, efficiency, and image quality improvements achievable by Dual Refocusing Echo Acquisition Mode (DREAM)-based B1+ shimming in whole-body magnetic resonance imaging (MRI) at 3T using the example of water/fat imaging. MATERIALS AND METHODS: 3D multistation, dual-echo mDixon gradient echo imaging was performed in 10 healthy subjects on a clinical 3T dual-transmit MRI system using station-to-station adapted B1+ shimming based on fast DREAM B1+ mapping. Whole-body data were obtained using conventional quadrature excitation and station-by-station adapted DREAM-based B1+ shimmed excitation, along with the corresponding B1+ maps for both excitation modes to assess image quality and radiofrequency (RF) performance. RESULTS: Station-dependent DREAM-based B1+ shimming showed significantly improved image quality in the stations covering the upper legs, pelvis, and upper body region for all subjects (P < 0.02). This finding is supported by corresponding B1+ maps showing an improved B1+ homogeneity and a more precise flip angle in the DREAM-based B1+ shimmed excitation (P < 0.01). Furthermore, the very short dual-channel DREAM B1+ mapping times of less than 2 seconds facilitate quick B1+ shimming. CONCLUSION: Station-dependent DREAM-based B1+ shimming improved RF performance and image quality and is therefore a promising technique for whole-body multistation imaging applications.
PURPOSE: To show the effect, efficiency, and image quality improvements achievable by Dual Refocusing Echo Acquisition Mode (DREAM)-based B1+ shimming in whole-body magnetic resonance imaging (MRI) at 3T using the example of water/fat imaging. MATERIALS AND METHODS: 3D multistation, dual-echo mDixon gradient echo imaging was performed in 10 healthy subjects on a clinical 3T dual-transmit MRI system using station-to-station adapted B1+ shimming based on fast DREAM B1+ mapping. Whole-body data were obtained using conventional quadrature excitation and station-by-station adapted DREAM-based B1+ shimmed excitation, along with the corresponding B1+ maps for both excitation modes to assess image quality and radiofrequency (RF) performance. RESULTS: Station-dependent DREAM-based B1+ shimming showed significantly improved image quality in the stations covering the upper legs, pelvis, and upper body region for all subjects (P < 0.02). This finding is supported by corresponding B1+ maps showing an improved B1+ homogeneity and a more precise flip angle in the DREAM-based B1+ shimmed excitation (P < 0.01). Furthermore, the very short dual-channel DREAM B1+ mapping times of less than 2 seconds facilitate quick B1+ shimming. CONCLUSION: Station-dependent DREAM-based B1+ shimming improved RF performance and image quality and is therefore a promising technique for whole-body multistation imaging applications.
Authors: Pengjiang Qian; Yangyang Chen; Jung-Wen Kuo; Yu-Dong Zhang; Yizhang Jiang; Kaifa Zhao; Rose Al Helo; Harry Friel; Atallah Baydoun; Feifei Zhou; Jin Uk Heo; Norbert Avril; Karin Herrmann; Rodney Ellis; Bryan Traughber; Robert S Jones; Shitong Wang; Kuan-Hao Su; Raymond F Muzic Journal: IEEE Trans Med Imaging Date: 2019-08-16 Impact factor: 10.048